Cain was not afraid of the Astral Sea as he had already visited one of the planes that existed there during his dreams. He had already seen the Dream World and was eager to visit it with his actual body since Beelze was currently there. No matter what, he was determined to find the young woman and find out her true nature.
As for greed, the Godslayer Humankind no longer offered him any help; if anything, they had become a burden. He honestly doubted he could find more lucky chances in this world, and his talent and foundation would stagnate if he did not leave.
A cultivator always needed to visit dangerous places full of treasure and lucky chances if they wanted to improve their talent and rise beyond their limits. No matter how strong Cain's foundation was, he was not impervious to stagnation.
